單項(xiàng)選擇題A gradual decrease in the discharge pressure of an operating hydraulic pump can be caused by ().

A.the four-way control valve failing to shift
B.the bleeder valve sticking in the open position
C.cold hydraulic fluid
D.a clogged air vent falter on the oil reservoir


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1.單項(xiàng)選擇題If you are given the job of adding hydraulic fluid to a mooring winch, and are not certain as to the type of fluid to use, you should ().

A.add fluid that is the same color as the fluid in the reservoir
B.add turbine oil because it is always a good substitute
C.add any oil that has the same viscosity as the hydraulic fluid
D.check the winch manufacturers instruction book

2.單項(xiàng)選擇題The output volume of a positive fixed displacement pump can be changed only by ().

A.changing the angle of the tilting plate
B.changing the speed of the pump
C.moving the slide block and rotor
D.moving the shaft trunnion block

3.單項(xiàng)選擇題An excessive charge of refrigerant in an air-cooled refrigeration system can cause ().

A.oil foaming in the compressor
B.higher than normal suction and discharge pressures with a higher box temperature
C.higher than normal discharge pressure with a normal box temperature
D.the compressor to run continuously

4.單項(xiàng)選擇題When the steering gear is in operation, you should ().

A.check hydraulic oil levels every hour
B.check the rams for overheating
C.check for excessive oil leakage from rams
D.drain water from telemotor cylinders each watch

5.單項(xiàng)選擇題The oil in a cargo winch gear box should be sampled periodically to ().

A.prevent the gear box from leaking
B.prevent the oil from becoming inflammable
C.make sure it has not become contaminated
D.make sure the motor bearings are lubricated

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The temperature differential occurring between the inlet temperature of the fluid to be cooled and the outlet temperature of the cooling medium in a shell-and-tube heat exchanger is greatest in which of the flow designs listed?()

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When a refrigeration compressor has developed a high head pressure as a result of a refrigerant overcharge, you should ().

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Heavy wear in a particular area of the inner circumference of a packing ring may be caused by ().

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The major source of chemical contaminants in hydraulic fluid is ().

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A pressure drop through the refrigerant liquid line may cause ().

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An increasing head pressure in a refrigeration system, without any corresponding change in the cooling water inlet temperature, would probably be caused by ().

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An internal bypass is provided on some hydraulic system suction strainers to help reduce the possibility of ().

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If the thermal bulb of an expansion valve is incorrectly placed at the center of the coil instead of the end, it will ().

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Which of the problems listed would came the discharge temperature of an R-12 refrigeration compressor to increase?()

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The rate of heat transfer between the hot and cold fluids passing through a shell-and-tube type heat exchanger will ().

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